DE2257519C3 - Process for the extraction of precious metals - Google Patents

Description

The invention relates to a method for the extraction of precious metals from parts of sulfide concentrates, Stone and the like. In particular, the invention relates to a better method for Extraction of platinum group metals from copper-containing raw materials.

In the following, the precious metals are referred to as EM for short, if necessary, and below this The term is then understood to mean gold and the six metals of the platinum group, namely platinum, palladium, Rhodium, ruthenium, osmium and iridium.

The platinum group metals normally occur naturally in sulphidic deposits together with base metals such as nickel, cobalt or copper. The total concentration of precious metals in different ores fluctuates quite a lot. At most, however, it is only a few ppm. The noble metals are normally extracted from such ores, regardless of their concentration, by first separating nickel, cobalt and copper. The mineral components present in the ore are generally first physically enriched and fused to form a stone. In the work up of the stone for the recovery of nickel, cobalt and copper ¹ at the same time other base metals, primarily iron, and the main amount of sulfur to be removed. The precious metals mainly remain in the residue as precious metal concentrate. That

^{3 4}

(Concentrate, however, is still predominantly separated from centrate. The precious metals are then dissolved in base metals and sulfur, even if the aqua regia, and the precious metal concentration remaining is higher than in the original residue and is practically free of metal,
spring stone. The first processing stage for the recovery of the noble metals consists in a method that consists in separating the base metals and sulfur under pressure with sulfuric acid, leaching by leaching the concentrate in a gradually decreasing amount of solids under pressure bandaged in an autoclave. The back precious metals are further enriched. Here, too, the mind contains elementary suspended solids are finally found in aqua regia, precious metals and gangue. You can work it up after leached, namely in a relatively small ία any known method, with single batch, whereby the noble metals in solution one sulfur and one similar to the one described above. Unfortunately, only some of the noble final concentrate of noble metals is dissolved in the process
metals, so that one has to further treat not only the above solution but also the preferred leaching residue described in the earlier application in order to obtain the noble leaching residue. ₁₅ lyes of copper have now shown that some

The main amount of precious metals in the concentrate copper and precious metals is likely to be practically

Concentrate in sulfide form. The imperfectly completely separate from each other, with other

However, leaching is mainly used, the concentrates of which, on the other hand, are rather precious metals

if not at all, on the present insoluble strongly dissolved out together with the copper

Precious metal oxides in the concentrate, which ao den. Therefore, to ensure that the separation of

a high temperature oxidation are formed. This copper and precious metals during the process

applies in particular to the roasting process, in which the chlorine leaching stage is also practically complete.

Ede'.metallzentrate normally during which runs continuously, you have to use additional processing means

Removal of base metals, primarily from turn on, which are the subject of the invention

Copper, to be subjected. If one now treats as should.

in addition to roasting, the stone and the concentrate The invention is thus primarily based on a

at some stage at high temperature with reduced process for the extraction of precious metals

ornamental conditions, or are in the starting ore from sulfidic, in particular from copper

If the precious metals are present, they can then be directed in the precious metal concentrates they contain. Further

Concentrate light precious metals in metallic form 30, a method is to be created according to the invention

be present, which do not soften with acid without which one can get out of such concentrates

Let the teres leach out. better separate the copper from the precious metals

How can the different precious metals in this pha-.

sen are adjusted and socialized with each other, the inventive method can be applied and which of these are soluble is not exactly known to the treatment of sulphidic noble metals. When leaching concentrate particles according to known process in general and in particular The precious metal concentrates obtained with king derer are applied to the treatment of precious metal water containing copper however, only gold, platinum and palladium concentrates work. According to the method according to the invention sufficient amount in solution. Rhodium, ruthenium, copper is separated from such particles, innium, Iridium and osmium, on the other hand, remain practically an advantage over the noble metals undissolved in the leach residue. readily oxidizing leaches, as it is in the above-mentioned

The aim of the invention is therefore to create an older German patent application Method of treating EM concentrates, is, or by using under oxygen pressure which is not only easier and more productive than sulfuric acid leaches. Both procedures will standing process, but in which one can more easily go to elemental sulfur-roasting without sulfidic sulfur can get along. In this way they form more oxidized than sulfate. The elemental sulfur no precious metal oxides insoluble in aqua regia. remains in the leached solid particles. If one proceeds according to the invention, all of them can be obtained from it in the usual way, Precious metals present in the concentrates practically The precious metals are then made up in aqua regia leached by aqua regia. You can solve 50 and can be obtained from this separately. Of the can therefore rely on a further, complex treatment which is an essential step of the present invention Dispense with leaching residue and receive a treatment in the process of conditioning the noble solution, from the sioh all precious metals in simple metal concentrate particles before the preferred from way to let win. leaching of copper by treatment

A characteristic of the present process 55 of the particles in a mineral acid in the presence of

The way of working is that you put it in the hydrogen sulfide. This allows the copper

copper present in the concentrate compared to the precious metal - better from the precious metal during the subsequent leaching

len preferentially leaches, as separate for the leachate metals.

process with chlorine applies, which in the older German The invention is explained in more detail with reference to the drawing

see patent application P 22 06 343.0 described 60 explained. It shows

is. This process stage replaces the previously known FIG. 1 is a generalized flow diagram of a separation of copper by leaching copper to extract precious metals from sulfiferous oxide using sulfuric acid from a roasted Danish material,

Concentrate, which is also insoluble in aqua regia. F i g. 2 a generalized flow diagram of the invented mowed Contains precious metal oxides. According to the method according to the invention.

As already mentioned, this differs in Elemental sulfur formed by fidic sulfur F i g. 1 procedure described by its besonnach any conventional process out of the cone of simplicity versus known processes. It

consists mainly of three consecutive or in situ by dissolving possibly in

Stages, namely a conditioning and processing of the iron and nickel present in the concentrate

An EdeJmetallzentrats, a subsequent sulfide is formed, or both means can be used

the leaching of precious metals with aqua regia at the same time. Copper and precious metals remain practically

and their extraction from the solution, namely in s tically undissolved, and they are therefore treated in the

advantageously in form; of the individual metals. (direct solid enriched The external supply of

_{The H 2} S used for the process according to the invention is not important. It is only essential that H ₂ S EM output concentrate can be of various original sources, so as to ensure that it is practical

jump and be composed in different ways. the total amount of precious metals and copper

The term precious metal concentrate is therefore to be found in the treated solids.

according to the invention any sulphidic, precious metal-containing copper and precious metals

Material understood, in which the value of the metal separated from each other, as shown in F i g. 1

the material extracted precious metals the costs and 2 is shown, by means of a controlled,

the treatment of the material to obtain this preferred oxidizing leaching of the treated

MetaUe exceeds. A nickel-copper brick with both solids. For example, this is suitable for this

for example 0.002% / · Noble metals are not inventively described in the earlier application cited at the beginning.

suitable noble metal concentrate. Bene process, after which solids and chlorine gas

The value of the total amount of noble recovered in an aqueous slurry introduces the copper

metals, with the assumption of 100% Ger-I ions in a carefully adjusted

containment and a reasonable total unity ao dox potential. The redox potential of the

tes of about 330 DM per ounce (31.1 g), the addition of chlorine and sludge increases

namely here only at around 220 DM per ton of stone. falls off by adding the solid particles. By

Compared with the cost of obtaining Nik- Controlling the rate of addition of the solid parts in

and copper alone, this is a very large amount. in relation to the rate of addition for the chlorine

After extracting the bulk of the in a 25 one can get the redox potential at or below the

such stone existing nickel and copper hold the selected potential at which the copper

The remaining solids, on the other hand, come from the solids preferentially over the noble

easily referred to as precious metal concentrates. metals is leached. At this stage of the procedure

Nickel anode loops with an EM concentration also benefit from the favorable influence of the previous one

tion of, for example, 0.1 ° / · result for the 30 acid-HjS treatment of the noble metals noticeable,

extracted precious metals have a value of about The separation of the copper from the precious metals

9,000 DM per ton, even under the leaching of sulphidic materials

would take EM recovery from only about 80 ° / e. Since this chlorine is best carried out with a redox

Amount required to treat the sludge for the Ge potential between about 450 mV and about 500 mV,

Extraction of these precious metals required costs 35 based on Pt-calomel electrodes. It was found

one can exceed this material and, of course, that the separation of the copper from the precious

also similar starting materials as EM concentrates metals in the subsequent leaching means

use for the method according to the invention. A chlorine runs practically completely when you do that

directly from a relatively strong precious metal EM concentrate first treated with acid-HjS Aul

containing ore mined nickel-copper-stone, the 40 in this way the precious metals remain, as with dei

for example 0.1 · / · noble metal and from the first stage, in the caustic residue and lie

Nickel or copper have not previously been separated off, naturally enriched there far higher. Without that

can therefore be used just as well as EM concentrate

turn amounts of precious metals together with the copper as if made of stone with a lower EM content

anode sludge obtained. He can therefore put the invention into solution. The redox potentials are in the fol

duly processed in a similar manner. always rely on Pt-saturated calomel electrodes

Precious metal ores can also be obtained as EM concentrates.

as an alternative to leaching with chlorine

meter by meter in the form of concentrates with relatively the treated solid particles, as in FIG. 2 shown

high density can be obtained. It is true that Kon- so also contain oxidizing leaching in other ways

central of this type nor low or even insignificant medium, for example by leaching under pressure;

trade quantities of nickel, cobalt, köpfer and end-HjSC ^ -containing liquids a and an oxygen

ICt gnmdmetauen, but you can still in overpressure, ch Saudi sulfur elemen

Advantageously, according to the invention, for the production of tar sulfur, wildly oxidized. The redox potential

are processed by precious metals. 55 of the stirred leaching schlamra will be as ready

As in Fig. 2 is schematically shown, this is mentioned above, aaf a value between approximately 450 mV EM concentrate first regulated in the form of a slurry and 500 mV. To melt the ge

In a mineral acid such as hydrochloric acid or in elemental sulfur that is formed, this is the rule

Sulfuric acid, in the presence of hydrogen sulfide the temperature is aaf below about 90 ^D C. De

conditioned. When using the preferred salt concentration, this is expediently about

acid, the conditioning is advantageously 10 atmospheres.

under conditions similar to those in the U.S.A. - The third stage is as shown in Fig.

Patent 3,085,054 for the leaching of a Nik- shown in a higher concentration of the noble

kd-Kopfer-Steins rait HQ are mentioned. To do this, metals are made by removing the bean from oxidizing the outlet

grind the concentrate finely, add the sulfur formed to the laogang residue with HO.

slurries and at a temperature of at least removed. The Ag of sulfur can be aaf ver

about 6O ⁰ C in the presence of H ₇ S treated. That was done in different ways. Works best now

Required H ₁ S is either supplied from the outside here under mild process conditions, inder

elemental sulfur is driven out of the solids at a low temperature, or by the Dissolves sulfur using highly selective solvents. The precious metals remain in highly concentrated form in the solid particles. At the same time, changes in the initial state of the precious metals, which normally occur under more severe treatment conditions, such as high-temperature roasting, are avoided.

The nadi removal of the main amount of the base metals and the sulfur bound to them in the original concentrate after the above three process stages obtained, highly precious metal-containing components

Transformation then takes place is not clear. However, the surprising fact remains that the Precious metals in the concentrate that are soluble when treated directly to remove the copper by selective copper leaching, among the same conditions are insoluble if the concentrate particles by the acid-HjS treatment preconditioned so that practically the total amount of precious metals after the preferred oxidizing ίο leach is present in the insoluble residue.

Another great advantage of the acid-H ₂ S treatment according to the invention is that nickel and other base metals, such as iron, which are less noble than copper, go into solution and thereby dissolve

concentrate is then leached in aqua regia. 15 copper, which together with the As a result, practically all of the precious metals present in the concentrate go out metals completely in solution. The solution obtained becomes it during the subsequent leaching of the copper is then separated for the recovery of the individual precious metals. The presence of base metals worked. like nickel and iron, in the concentrate, decreased

As already mentioned, the implementation of the »0 or avoids the need for an external process without the preceding acid feed of H ₂ S for the acid HS treatment, since then H ₂ S conditioning is carried out during the treatment of some EM Dissolution of the soluble base metal sulfides Concentrates for the dissolution of precious metals while H ₂ S is formed in situ.

rend the following preferred oxidizing Another benefit of acid-H ₂ S treatment

Lead leaching of copper. Why precious metals »5 are easier to remove when leached with aqua regia with some concentrates are noticeable. Due to the fact that when leaching out the copper as with others, and as with the process according to the invention, the noble metals contribute to the acid-H ₂ S treatment that the metallic as well as oxidized or sulfidic noble metals become less soluble, is instant - Shape before treatment with aqua regia in the borrowed not clear. However, the answer to this should be that in some concentrates originally in EM-insolubility, noble metals are present at least partly in memetallic form, which can be traced back to oxides. If this is the case, during the acid-H ^ conditioning treatment, then the process according to the invention will even be converted into sulfides. Such an eleven then an advantage, if the original EM-fect could be responsible for the improved concentrates contain no base metals, since the separation of the copper from the noble metals with the metals by the previous, inventive oxidizing leaching, which of the acid-H ₂ S-Be-Acid-HjS-Conditioning converted into sulphides follows, since, as in the cited old application, so that practically all existing applications are mentioned, copper sulphide is dissolved in aqua regia by precious metals. An EM concentration with chlorine is better to separate from the noble metals 40 without any base metals is extremely impossible if the noble metals are likely to be in sulfidic form, but the example can easily be mislaid instead of in metallic form. That noble metals apply to the understanding of type, influence and amin metallic form just as well as in sulphidic application of the method according to the invention. The present invention is illustrated by the examples

by treating nickel and copper ores to 45 explained.

Extraction of nickel and copper, example 1

understand which ores are based on treatments

during the extraction of nickel, cobalt and This example shows the case of treating a

Experience copper. '' EM concentrate according to the present process,

If one fuses such an ore into so , for example, but without the previous acid-HjS-conditioning- «aem stem, then there is a certain amount of nickel, rang. A nickel-copper-cobalt and Köpfer generally in metallic form is used as the EM concentrate, which has the main amount of nickel and form. Since the precious metals in turn with nickel, copper has already been withdrawn. The nickel is associated with cobalt and copper, so electrolytic refining of soluble nickel can be obtained. The nickel anode sludge cobalt and copper is present, which is melted down for the production of new anodes, amg of nickel, cobalt and copper from a solid which is then formed again for the extraction of further nickel and the precious stone. be electrolyzed. The new metals obtained in this way are in metallic form. Whether these precious metals in anode sludge are ultimately used as EM-Konnietalhscher form noble metals by 60 centrate used for this example :

Cu Ni Fe Co S. SiO, EM 46 5 4th 1 16 25th 2

509611/24)

The above concentrate is leached out by means of chlorine at a certain redox potential, namely according to the method described in the earlier German patent application no. P 22 06 343.0 mentioned, so as to selectively dissolve the base metals with respect to the precious metals. The redox potential is held at about 450 mV, a value used in experiments with other concentrates of similar composition according to the precious metals practically completely undissolved in the residue of the chlorine leaching lag behind. In the present case, however, the following percentages of metal dissolve:

Au Pt Pd Rh Ru Ir <1 1.3 1.0 11th 30th 28

10

Example 2

A result similar to Example 1 is obtained if an EM concentrate similar to Example 1 is roasted and reduced with hydrogen before it is leached with chlorine under conditions similar to Example 1. The EM-concentrate is roasted at this 75O ⁰ C and reduced at 500 ⁰ C with hydrogen to give a material with the following composition in percent by weight:

Cu Ni Fe S. PMs 71 8th 3 2 1.6

This material is leached at different redox potentials using chlorine, with the following Percentages of the various precious metals go into solution:

Redox
mV Au Pt Pd Rh Ru Ir 450
475
500 0.03
0.09
<0.07 0.05
0.07 <0, l
<0, l
<0, l 3.7
4.8
8.0 0.9
1.4
8.2 2
4th
8th

Gold, platinum and palladium remain practically undissolved, the other metals However, platinum groups strongly dissolve even at 450 mV. Because this concentrate as a result of the reduction treatment with high probability contains precious metals in metallic form - one can reasonably conclude that the similar dissolution behavior of the noble metals in Example 1 at least is partly due to the fact that the precious metals in the concentrate are in metallic form are present.

Example 3

In contrast to the above examples, you get a completely different result if you use a similar concentrate melts into a stone before leaching with chlorine. The EM concentrate has in this one Case the following composition in percent by weight:

50 Au

Pt

Pd

Rh

Ru

Approx Ni Fe S. SiO, Em 46 8th 4th 14th 8th 1.2

55

This concentrate is fused with iron sulfide and borax, and the stone obtained here has the following composition in percent by weight

Approx Ni Fe S. SK) ₁ A 54 7th 4th 20th <1 1.6

0.4 I -

As in Example 1, gold, platinum and palladium practically do not go into solution. It is noteworthy, however, that rhodium and ruthenium also remain practically undissolved. If the leaching of rhodium and ruthenium in the preceding cases is at least partly due to the fact that they are in metallic form in the concentrates, then the fact that they are insoluble in the present case must probably be due to their conversion to sulfides by the process of Stone melting can be returned. It therefore looks as if the precious metals in the concentrates would have to be in sulphide form if one would like to avoid leaching out of the precious metals from the corresponding concentrates when leaching with chlorine. Irrespective of this, however, the fact remains that the noble metals can practically be prevented from dissolving out during the leaching with chlorine if the method is carried out according to the invention, as is shown in the following examples.

Example 4

Again, the EM concentrate of the same origin is used, which together are similar is set, like those of the previous example, what from the following, given in percent by weight analysis shows:

The stone obtained in this way is leached with chlorine at a redox potential of 475 mV. the different precious metals go into solution as follows:

Cu Ni Fe S. SiOi EM 52 4th 4th 17th 12th 1.6

Instead of a direct leaching with chlorine, or a roasting, reducing or melting of a stone before leaching with chlorine, the concentrate is first _{conditioned in this case with HCl in the presence of H 2} S according to the invention.

A slurry of a solution containing 200 g / l HCl is ^{treated for 20 hours at 65 °} C. in the presence of H ₂ S, which is introduced into the slurry at a rate of about 10 ml / min. Here, nickel and iron go into solution, while the main amount of copper and practically the entire amount of precious metals remain in the solid particles, as shown by the following, percentages dissolved:

Cu Ni Fe Au Pt Pd Rh Ru Ir 3 61 73 <0.05 <0.07 <0.07 <0, l <O, 35 <0, l

The solids are then leached with chlorine to separate the copper from the precious metals. For this purpose, a slurry of 100 g / l solids in an originally 20 g / l HCl and 5 g / l treated monovalent copper-containing solution for about 4.5 hours at 97 ° C, with one in the Solution at a rate of 80 ml / min.

Introduces Cl ₂ and keeps the redox potential at a maximum of 475 mV. About 90% of the base metals go into solution, while the noble metals again remain practically completely in the solids, as can be seen from the following dissolved amounts given in%>:

Cu Ni Fe Au Pt Pd Rh Ru Ir 95 85 90 0.1 0.7 0.7 0.2 1.0 0.3

The residue remaining after this process stage has about 30 ⁰ O of the weight of the original EM concentrate and is composed in percent by weight as follows:

Cu Ni Fe S. Au Pt Pd Rh Ru Ir Total
EM 10 1 0.5 42 0.6 1.9 1.8 0.7 0.4 0.3 5.7

The elemental sulfur present in this material is removed, in this case by reaction with sodium sulfite in an aqueous solution, with sodium thiosulfate being formed. For this purpose, a suspension of the solids in the solution is kept at 65 ° C. for several hours, using about a 10% excess of sodium sulfite. The final pH is 7.5. Some of the noble metals dissolve, but the solution is acidified after the solids have been separated off, and so the main amount of the noble metals originally dissolved is precipitated _{by the reducing effect of the SO 2 formed when the acid reacts with excess sodium sulfite.} The solids remaining after the sulfur has been removed therefore contain practically all of the precious metals and are made up in percent by weight as follows:

Cu Ni Fe S. SiOt Au Pt Pd Rh Ru Ir Total
EM 12th 2 1 10 3i 1.0 3.8 3.2 1.2 0.7 0.6 10.7

The material obtained in this way is leached in aqua regia, which removes the precious metals solve practically completely, which is evident from the following table given in ° / o:

Au Pl Pd Rh Ro Ir 99.0 99.0 99.0 95.0 98.0 94.0

The residue remaining after the noble metals have been dissolved out has the following composition ii Weight percent:

Approx Ni Fe SiO, Au Pl Pd Rb Bn Ir 0.1 0.7 1.3 60.0 0.03 0.11 <0.1 <0.2 <0.03 <0 *

This residue is returned to the production of new quantities of EM concentrate, and the dissolved precious metals are independently recovered from the solution by known methods.

In this way, a concentrate containing precious metals, which has been shown to be easy to choose by means of selective copper leaching Chlorine dissolves, advantageously according to the invention Process conditioned The same precious metals are thereby under the conditions selective leaching of copper by means of chlorine is insoluble. They are also practically complete soluble in aqua regia. As a result of this remarkable effect, the method according to the invention is for the extraction of precious metals from concentrates much easier and more productive than known ones Procedure. In addition, it can generally be applied to EM concentrates of various origins, as shown in the following example.

Example p

The EM concentrate used for this is made directly from an EM ore in the form of a nickel-copper stone obtained with the following composition in percent by weight:

5
Ni Cu Fe S. EM 37 20.5 9.9 27.0 ~ 0, l

IO The stone is ground to a grain size of 0.15 mm, at a rate of 10 g / Mi α. slowly added to an alkali solution that is 280 ji / 1

Contains HCl and 30 g / l Ni, and while stirring, 60 ⁰ C and a concentration of 200 g stone piro liter solution converted The H ₂ S is formed in situ by dissolving nickel and iron from the stone. until practically that

so the total amount of nickel and iron and about 75 ¹ Vo of the stone have gone into solution. The various metals dissolve in the following%:

Ni Cu Fe Au Pt Pd Rh Ru Ir 99.8 1.0 99 0.4 0.2 <0.5 0.8 <0.5 1

The total amount of copper and precious metals remains practically unsolved. The remaining one Solid is made up in percent by weight as follows:

Ni Cu Fe S. BM 0.7 73.2 0.5 18.6 ~ 0, l

These solids are then leached with chlorine. The concentration of solids in the slurry is 100 g / l. Discarded for leaching

det one a solution with 50 g / l Ni, 50 g / l HCl and 5 g / l copper. Chlorine is poured into the slurry at a rate of 70 ml / min, keeping the temperature at 100 ° C and adjusting the redox potential to 430 mV. Go here about 77% of the solids in solution, and the following percentages of the various metals solved:

Cu Ni Fe Au Pt Pd Rh 'Ru Ir 99 25th 50 <0.2 <0, l <0.5 0.8 1.0 -

At this stage of the process, the water is practically leached out, with the following percentages all copper dissolved out, while the precious metals of the precious metals go into solution: in turn remain almost completely in the solid phase, the following composition in percent by weight has: 55

Ni

1.4

Fe

1.0

77

EM

Au Pt Pd Rh Ru Ir > 99 > 97 > 98 98 > 98 > 90

The one remaining after aqua regia leaching Residue weighs only about 0.5% of the original EM concentrate, and it contains

About 85 V. of the sulfur are in elemental form the weight percentage of the following precious metals: present, and they are made with carbon disulfide

removed at 20 ⁰ C without loss of precious metals. 65 _Au results in a total decrease in weight of approx

78 · / .. · -

The solids obtained are then in Königs- < 0.01

Pt

<0.03

Pd

Rh

0.2

Ru

<0.03

This residue consists almost entirely of SiO _s and other types of gangue. It can be easily recycled and used to make additional quantities of EM concentrate. The procedure and result of the treatment described in this example are practically similar to those of the preceding examples, although the EM concentrates used as starting material come from different sources in both cases, are produced by different processes, and differ greatly in their composition.

Example 6

The influence of the acid-HjS pretreatment on the dissolution behavior of the noble metals during the subsequent leaching of copper is shown on the basis of the following three pairwise experiments in which different EM concentrates with different sulfur contents are used. In one trial of each trial pair, one works directly with a Clj lye without prior conditioning, while in the other trial one first pre-leaches with HCl — HgS and then leaches with CIo. The first two EM concentrates referred to below are similar to those of Examples 1 through 4. The third Kt * - concentrate

ίο provides a low-sulfur fraction . EM stones similar to that of Example 5. The HCl — H, S and Cl ₂ LaUgUBg are each duich performed under conditions similar to those already described, with one for leaching using CL, in all cases with a redox -Potential of 450 mV is working. Leaching with Cl ₂ causes the following amounts of precious metals to dissolve:

EM concentrate similar to I * oS

Lye treatment

Dissolution of EM after leaching with Ot in · / · Au Pt Pd j Rh I Ru I Tr

Example 1 to 4 ..
Example 1 to 4 ..
Example 5

19.8
13.6
14.2

directly with Cl,
beforehand with HCl-H ₄ S

directly with CU
beforehand with HCl-H ₂ S

directly with Cl ₂
beforehand with HCl-H ₀ S

<0.01
<0.02

<0.04
0.02

0.3
0.3

1.04
0.04

<0.02
0.02

0.04
1.2

0.05
0.08

0.08
0.03

0.02
1.2

0.6
1.0

2.1
0.5

49
<3.3

2, «
1.4

17.5
2.3

27
1.7

3.0
1.3

16.7
1.5

25th
1.6

This clearly shows that the amount of Au, Pt and Pd leached out is negligible in all cases, _{whereas the amount of Rh, Ru and Ir leached out in the direct leaching with Cl 2 is} quite considerable, in particular for experiments No. 2 and 3, although this amount is significantly reduced by the previous HCl — H ₂ S leaching, in particular in experiments No. 2 and 3. Since starting materials with a relatively low sulfur content are used for this in both cases, which are therefore probably correspondingly more Containing material in metallic form, the stated values agree with the previously established hypothesis that noble metals present in metallic form _{dissolve out to a greater extent when leached with Cl 2} than noble metals present in sulfidic form, and that the influence of the Acid-H ₂ S treatment to reduce the leaching out of the noble metals during the subsequent leaching with Cl _{2 is} due to the unexplained conversion of such metals into sulfides. The HCl — H ₂ S treatment therefore has less of an effect on the behavior of concentrate No. 1 during the leaching by means of Cl ₂ than that of concentrate No. 2 or 3, since in concentrate No. 1 the amount of noble metals in sulphide form is greater than in concentrates No. 2 or No. 3. The treatment according to the invention with HCl — H ₂ S influences the optimal separation of the copper from the noble metals to a far greater extent than is the case with most concentrates by leaching with Copper alone can achieve a certain redox potential.

Example 7

This example shows the influence of the process according to the invention when the copper is separated from the noble metals by leaching with sulfuric acid under excess oxygen pressure, and not by leaching with chlorine, as in the previous examples. For this purpose, an EM concentrate similar to Examples 1 to 4 is leached under pressure with sulfate, both with and without prior conditioning with H ₂ S and according to a batch process. For this purpose, about 500 g of solids are scraped up in 4 l of a solution which originally contains 150 g / l of H ₂ SO ₄ , and under an oxygen pressure of 10 atm. treated at a temperature below 90 ° C in order to avoid melting of the elemental sulfur formed during leaching. The initial redox potential is about 200 mV and it increases gradually in the course of the leaching. As soon as the redox potential has reached a value of 480 mV, the process is stopped and the leached solids are »separated off from the leaching solution.

The analyzes of the unconditioned and conditioned EM concentrates in percent by weight are as follows:

Cu Ni Fe S. EM Unconditioned EM concentrate
Conditioned EM concentrate 57.7
71.0 3.0
<0.5 2.6
0.3 15.9
22.0 1.65
1.93

509611/248

The conditioning of the original concentrate with H ₂ S is carried out in a solution containing hydrochloric acid, as a result of which iron and nickel are dissolved out in the values given above.

Unconditioned
EM concentrate

Confectionery ordered
EM concentrate

Cu

99
99

Ni

74
97.5

This clearly shows that the conditioning leads to a considerable reduction in the amount of leached precious metals leads, in particular for Rh, Ru and Ir.

Those skilled in the art of EM metallurgy will recognize that the foregoing are preferred modes of operation for the recovery of precious metals from concentrates according to the invention are described. The biggest The difference between the method according to the invention and known methods is that roasting and leaching with sulfuric acid to separate the copper from the precious metals the selective leaching of copper is replaced. The oxidation of the precious metals that occurs during roasting comes, and prevents their subsequent dissolution in aqua regia, is thereby avoided.

The percentages of pressure sulphate leached from both materials Metals are as follows.

Au

<0.04
<0.02

Pt

<0.04
<0.03

Pd

<0.04
<0.04

Rh

3
1

Ru Ir 10 9 7th 2.5

In this way, according to the invention, precious metals are practically completely dissolved in aqua regia. When copper is leached directly from some EM concentrates, a certain amount of precious metals will dissolve. In contrast , it is inventive

a. duly possible, through the controlled leaching of copper from EM concentrates in specific Way to reduce or practically avoid such a leaching of precious metals. The EM concentrate is therefore according to the invention in

Acid solution conditioned in the presence of H ₂ S, as described above, and a leaching out of the noble metals in the subsequent oxidizing leaching of copper is advantageously and surprisingly reduced or even completely reduced.

avoided.

For this purpose 2 sheets of drawings

Claims (10)

Patent claims: 1. Process for the extraction of precious metals from solid particles of copper containing, precious metal containing stones and sulphide concentrates, by stirring the suspended solid particles in an aqueous, oxidizing alkali solution, characterized in that one (1) the solids before leaching in the form of a slurry with stirring in a mineral acid-containing solution in the presence of hydrogen sulfide and conditioned (2) the slurried conditioned solids in said oxidizing caustic solution at or below a selected redox potential at which the in the solids present copper compared to the precious metals contained therein ao is preferably leached. 2. The method according to claim 1, characterized in that the mineral acid is hydrochloric acid or sulfuric acid is used. 3. The method according to claim 2, characterized in indicates that, based on the total amount of leaching of all soluble components from the solids in the conditioning solution necessary amount, an excess of Hydrochloric acid used. 4. The method according to claim 3, characterized in that a Siein is used, which contains nickel and / or iron as a base metal in addition to copper, nickel and / or iron leaches the solid particles by treatment in hydrochloric acid solution while the solids at the same time conditioned for the subsequent separation of the copper from the precious metals will. 5. A method for oxidizing leaching 4 »according to claim 1, characterized in that man (1) the conditioned solids in the form of a slurry with stirring in a Copper-I-ion-containing chloride solution with chlorine leaches, and (2) the redox potential by controlling the rate of addition of chlorine as a function on the rate of addition of the solids to the slurry. 6. The method according to claim 5, characterized in that stone is used as solid particles with at least nickel or iron used as a further base metal that one is used as a mineral acid Hydrochloric acid used in excess, based on never total amount of necessary to leach out all acid-soluble components from the solids in the conditioning solution Amount, with the additional base metal being leached out by the hydrochloric acid and at the same time the solids for the subsequent separation of the copper from the precious metals be conditioned. 7. The method according to claim 6, characterized in that that he (1) separates the leached solids from the oxidizing caustic solution, (2) Removed the elemental sulfur from the leached solids and so removed the precious metals further enriches in the remaining solids,. . (3) leaches the remaining solids in aqua regia, thus dissolving the precious metals and (4) Recovers the precious metals from the solution. 8. The method according to claim 1, characterized in that the suspended conditioned solids are leached with stirring in a solution containing sulfuric acid under excess oxygen pressure .OAA I. 9 The method according to claim 8, characterized in that stone is used as solid particles with at least nickel or iron used as a further base metal that one is used as a mineral acid excess hydrochloric acid used, based on ώε total amount of the Leaching of all acid-soluble components from the solids of the conditioning solution is required Amount, and that the other base metal is leached by the hydrochloric acid while at the same time the solids for the subsequent separation of the copper from the precious metals be conditioned. 10. The method according to claim 9, characterized in that one (1) separates the leached solids from the oxidizing caustic solution, (2) Removed the elemental sulfur from the leached solids and so removed the precious metals further enriches in the remaining solids,. (3) the remaining solids in aqua regia leaches and so dissolves the precious metals and (4) Recovers the precious metals from the solution.